Mycophenolate Mofetil Treatment of Systemic Sclerosis Reduces Myeloid Cell Numbers and Attenuates the Inflammatory Gene Signature in Skin

Fewer than half of patients with systemic sclerosis demonstrate modified Rodnan skin score improvement during mycophenolate mofetil (MMF) treatment. To understand the molecular basis for this observation, we extended our prior studies and characterized molecular and cellular changes in skin biopsies from subjects with systemic sclerosis treated with MMF. Eleven subjects completed ≥24 months of MMF therapy. Two distinct skin gene expression trajectories were observed across six of these subjects. Three of the six subjects showed attenuation of the inflammatory signature by 24 months, paralleling reductions in CCL2 mRNA expression in skin and reduced numbers of macrophages and myeloid dendritic cells in skin biopsies. MMF cessation at 24 months resulted in an increased inflammatory score, increased CCL2 mRNA and protein levels, modified Rodnan skin score rebound, and increased numbers of skin myeloid cells in these subjects. In contrast, three other subjects remained on MMF >24 months and showed a persistent decrease in inflammatory score, decreasing or stable modified Rodnan skin score, CCL2 mRNA reductions, sera CCL2 protein levels trending downward, reduction in monocyte migration, and no increase in skin myeloid cell numbers. These data summarize molecular changes during MMF therapy that suggest reduction of innate immune cell numbers, possibly by attenuating expression of chemokines, including CCL2.

Modulating therapeutic antitumor T cell immunity with MicroRNAs (156.21)

MicroRNAs are attractive candidates for enhancing the therapeutic effectiveness of adoptive T cell therapy, although overcoming tumor-induced immunosuppression in the tolerogenic ovarian cancer microenvironment remains a formidable barrier. We hypothesized that over-expression of miR181a in adoptively transferred tumor-reactive T cells would result in sustained anti-tumor immunity within the tolerogenic ovarian tumor microenvironment. To test this, congenic tumor-reactive T cells were intraperitoneally injected into mice bearing established transplantable ovarian tumors. Twelve and 26 days post-transfer, RNA was isolated from sorted peritoneal host or transferred CD4 and CD8 T cells. Contrary to our initial hypothesis, miR181a expression was significantly and exponentially greater in transferred CD4 and CD8 T cells, compared to host-derived T cells at these temporal points during which the function of transferred T cells was impeded by the tolerogenic microenvironment. This suggested an unexpected negative role for miR181a in the context of T cell immunotherapy. To confirm these findings, T cells over-expressing miR181a were adoptively transferred into tumor-bearing mice and survival was monitored. Compared to mice receiving either non-transduced or control-vector transduced T cells, mice treated with T cells over-expressing miR181a had significantly reduced survival, supporting the novel finding that miR181a may have a negative role in adoptive T cell immunotherapy.

Harnessing the effect of adoptively transferred tumor-reactive T cells on endogenous (host-derived) antitumor immunity

Adoptive T cell transfer therapy, the ex vivo activation, expansion, and subsequent administration of tumor-reactive T cells, is already the most effective therapy against certain types of cancer. However, recent evidence in animal models and clinical trials suggests that host conditioning interventions tailored for some of the most aggressive and frequent epithelial cancers will be needed to maximize the benefit of this approach. Similarly, the subsets, stage of differentiation, and ex vivo expansion procedure of tumor-reactive T cells to be adoptively transferred influence their in vivo effectiveness and may need to be adapted for different types of cancer and host conditioning interventions. The effects of adoptively transferred tumor-reactive T cells on the mechanisms of endogenous (host-derived) antitumor immunity, and how to maximize their combined effects, are further discussed.

Immunosuppressive Ovarian Cancer-Infiltrating Dendritic Cells can be transformed into Immunostimulatory Cells through In situ CD40 and Toll-like Receptor 3 Stimulation (100.32)

The individualized targeting of tumor-induced immunosuppression may contribute to the advancement of therapy against lethal epithelial tumors. We find that in a newly developed transgenic model of ovarian cancer, CD11c+MHCII+ dendritic cells are the most abundant leukocyte subset at tumor sites from early tumorigenesis. We also demonstrate (using a transplantable tumor model) that in the ovarian carcinoma microenvironment, these cells spontaneously engulf tumor materials and instead of promoting anti-tumor immunity, suppress T cell function. In situ co-stimulation of CD40 and Toll-like receptor (TLR) 3 on tumor-infiltrating dendritic cells reduced their L-arginase activity as well as enhanced their production of pro-inflammatory cytokines, augmented their capacity to process antigens, and up-regulated costimulatory molecules in vivo in mice and in vitro in human dissociated tumors. Correspondingly combined CD40/TLR agonists boosted measurable T-cell-mediated antitumor immunity and induced the rejection of otherwise lethal ovarian carcinomas. These results underscore the potential of transforming tumor-infiltrating dendritic cells from an immunosuppressive to an immunostimulatory cell type. Lastly, combined administration of synergistic CD40 and TLR3 agonists could enhance their individual therapeutic effects against ovarian and other lethal epithelial cancers.

Adoptive co-transfer of tumor specific CD4+ T cells awakens host protective immunity to MHC-II- ovarian cancer through CD40-mediated licensing of dendritic cells and CCL5 secretion. (131.14)

The effect of adoptive cell transfer (ACT) on endogenous anti-tumor immunity remains largely unknown. We previously showed that transferring tumor-primed T cells into tumor-bearing mice awakened endogenous antitumor mechanisms and induced the rejection of otherwise lethal ovarian cancers when coupled with depleting tumor-associated immunosuppressive dendritic cells (DCs). Here we elucidate this arousal of host responses to be due to the licensing of host DCs by co-transferred CCL5-secreting CD4+ T cells that recruit host antitumor immune cells. Tumor-primed CD4+ T cells significantly delayed tumor progression and directly activated host tumor-resident DCs which subsequently activated tumor-exposed C8+ T cells. These effects were long-lived, as host T cells obtained from mice treated with ACT were protective against secondary challenge with the same tumor. Disrupting CD40-CD40L interactions during ACT impaired DC maturation and ability to stimulate tumor-infiltrating CD8+ T cells. Similarly, abrogating CCL5 secretion reduced DC maturation and the survival increases obtained from ACT. The absence of CCL5 and CD40 further reduced the protective phenotype of the host cells against secondary challenge with the same tumor. Our data unveil a CD40-dependent mechanism of transferring immunity from adoptively transferred CCL5-secreting CD4+ T cells to host immune cells, causing sustained antitumor effects, and advance the field towards developing more potent anti-tumor therapies.

Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity

The success of clinically relevant immunotherapies requires reversing tumor-induced immunosuppression. Here we demonstrated that linear polyethylenimine-based (PEI-based) nanoparticles encapsulating siRNA were preferentially and avidly engulfed by regulatory DCs expressing CD11c and programmed cell death 1-ligand 1 (PD-L1) at ovarian cancer locations in mice. PEI-siRNA uptake transformed these DCs from immunosuppressive cells to efficient antigen-presenting cells that activated tumor-reactive lymphocytes and exerted direct tumoricidal activity, both in vivo and in situ. PEI triggered robust and selective TLR5 activation in vitro and elicited the production of hallmark TLR5-inducible cytokines in WT mice, but not in Tlr5-/- littermates. Thus, PEI is a TLR5 agonist that, to our knowledge, was not previously recognized. In addition, PEI-complexed nontargeting siRNA oligonucleotides stimulated TLR3 and TLR7. The nonspecific activation of multiple TLRs (specifically, TLR5 and TLR7) reversed the tolerogenic phenotype of human and mouse ovarian tumor-associated DCs. In ovarian carcinoma-bearing mice, this induced T cell-mediated tumor regression and prolonged survival in a manner dependent upon myeloid differentiation primary response gene 88 (MyD88; i.e., independent of TLR3). Furthermore, gene-specific siRNA-PEI nanocomplexes that silenced immunosuppressive molecules on mouse tumor-associated DCs elicited discernibly superior antitumor immunity and enhanced therapeutic effects compared with nontargeting siRNA-PEI nanocomplexes. Our results demonstrate that the intrinsic TLR5 and TLR7 stimulation of siRNA-PEI nanoparticles synergizes with the gene-specific silencing activity of siRNA to transform tumor-infiltrating regulatory DCs into DCs capable of promoting therapeutic antitumor immunity.

CCL5-mediated endogenous antitumor immunity elicited by adoptively transferred lymphocytes and dendritic cell depletion

Adoptive transfer of antitumor T cells is a promisingly effective therapy for various cancers, but its effect on endogenous antitumor immune mechanisms remains largely unknown. Here, we show that the administration of naive T cells de novo primed for only 7 days against tumor antigens resulted in the durable rejection of otherwise lethal ovarian cancers when coupled with the depletion of tumor-associated immunosuppressive dendritic cells (DC). Therapeutic activity required tumor antigen specificity and perforin expression by the adoptively transferred T cells, but not IFN-gamma production. Importantly, these shortly primed T cells secreted large amounts of CCL5, which was required for their therapeutic benefit. Accordingly, transferred T cells recruited CCR5(+) DCs into the tumor, where they showed distinct immunostimulatory attributes. Activated CCR5(+) host T cells with antitumor activity also accumulated at tumor locations, and endogenous tumor-specific memory T cells remained elevated after the disappearance of transferred lymphocytes. Therefore, persistent, long-lived antitumor immunity was triggered by the administration of ex vivo activated T cells, but was directly mediated by immune cells of host origin. Our data unveil a CCL5-dependent mechanism of awakening endogenous antitumor immunity triggered by ex vivo expanded T cells, which is augmented by tumor-specific targeting of the cancer microenvironment.